Valve assembly for fluid motors and the like



Oct. 28, 1969 H. H. SCHMIEL 3,474,708

VALVE ASSEMBLY FOR FLUID MOTORS AND THE LIKE Filed Jan. 17, 1968 '2 Ex? /|5 5 ,6 |4k n I '7 om o o m o 8i ||i 7 o o o 0 U if -em i a 35 5 .5 MENTOR HERBERT H. .SCHM/EL BY 5% fimwull? e, W

ATTORNEYS;

United States Patent US. Cl. 91-436 Claims ABSTRACT OF THE DISCLOSURE Valve assembly for double acting fluid motors as used, for example, in raising and lowering an earth moving scraper bowl or like implement to enable rapid power lowering of the implement for quick dumping of a load therein at a rate which may exceed the capacity of the fluid supply pump.

BACKGROUND OF THE INVENTION In general, it is known to provide in conjunction with a directional control valve for a double acting fluid motor a so-called makeup check valve which communicates the return circuit with the pressure circuit when pressure in the latter is less than that in the return circuit. In this type of makeup circuit, the return circuit downstream of the directional control valve member is blocked when there is such reduction in pressure circuit pressure. In this Way, cavitation of the pressure circuit is prevented.

It is also known to provide a check valve between the directional control valve and the motor which opens to permit drawing of additional fluid from the tank in the event of dropping of pressure in the motor during lowering of a heavy load thereon as in conjunction with a fork lift truck or the like. In such installation there may be provided another check valve which, when the return line to the reservoir is blocked at the directional control valve, will open communication between the return line and the pressure supply line to enable actuation of the motor at a rapid rate when there is little or no load thereon.

SUMMARY OF THE INVENTION In the present invention the valve assembly is preferably arranged to be mounted directly on one end of the fluid motor, whereby the directional control valve may be a conventional four-way open center valve of the spool type, for example, having three or four positions such as neutral, raise, and lower, and a float position as the fourth position, if desired.

One object of this invention is to provide a valve assembly of the character indicated wherein a pressure seated check valve is opened by a flow responsive pilot valve to return displaced fluid to the motor whenever the rate of flow of incoming fluid exceeds a predetermined value, thus to eliminate cavitation of the motor and to provide for quick dumping as in the case of an earth moving scrapper bowl or like implement.

It is another object of this invention to provide a valve assembly of the character indicated wherein a check valve is provided between the pressure and return sides of the motor to prevent flow of fluid in that direction when the rate of flow of fluid into the motor is less than that required to open the aforesaid pressure seated check valve.

It is another object of this invention to provide a valve assembly of the character indicated wherein the housing thereof has a passage to intercommunicate the ports of a double acting fluid motor, there being oppositely disposed check valves therein operative upon predetermined rate of flow of fluid into the motor to be opened to con- 3,474,708 Patented Oct. 28, 1969 duct returning fluid back into the motor and being operative to prevent reverse flow of fluid whenever the rate of flow of fluid into the motor is less than a predetermined amount.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicatve, however, of a few of the various ways in which the principle of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of a hydraulic circuit embodying the present invention;

FIG. 2 is a cross-section view on enlarged scale taken substantially along the line 2-2, FIG. 1; and

FIG. 3 is a fragmentary cross-section view illustrating a modification.

DISCUSSION OF THE. INVENTION Referring to FIG. 1, the reference numeral 1 denotes a differential displacement double acting fluid motor, the piston rod 2 of which is adapted to be linked to an earth moving scraper bowl or the like, so that when the piston 3 is raised in the cylinder 4, the scraper bowl or like implement is raised to lift a load therein, and when the piston 3 is lowered, the implement is lowered either to engage the earth to perform its scraping operation or to dump a load of earth therein. The valve assembly 5 constituting the present invention is attached to the head end of the cylinder 4 and is provided with two ports 6 and 7 leading, as presently to be described in detail, into the head end of the cylinder 4. The plate at the rod end of the cylinder 4 is provided with a port 8 leading into the rod end of the cylinder 4.

The rest of the hydraulic circuit of FIG. 1 (except for spool 16 reciprocable therein to communicate the pressure inlet port 14 with the return port 17 when the spool is in its neutral N position. The directional control valve 15 has, in addition, two motor ports 18 and 19 which are connected by means of the respective conduits 20 and 21 t0 the respective motor ports 7 and 8 and, in addition, the conduit 21 has the branch line 9 connected to the port 6 of the valve assembly 5.

When the valve spool 16 is in its neutral N position, the ports 18 and 19 are blocked thereby so that the piston 3 will remain in the position to which it was last actuated. When the valve spool 16 is shifted to the raise R position fluid under pressure is conducted from the inlet port 14 to the upper motor port 19 thus to act on the rod end of the piston 3 to raise the same in the cylinder 4, and the oil 14 will be communicated with the lower motor port 18' whereby fluid under pressure will be conducted into the head of the cylinder 4 via conduit 20 and port 7 to cause the piston 3 to move downwardly, and the oil displaced from the rod end is conducted to the tank via the port 8, conduit 21, upper motor port 19, and return port 17.

If desired, the directional control valve may be provided with a float F position at which the spool 16 intercommunicates the lower and upper motor ports 18 and 19 with each other and with the tank port 17, and in that case, the piston 3 may float in the cylinder 4, that is, if it is in the upper position it may gradually descend with oil from the rod end flowing into the head end together with makeup oil from the tank 10 flowing through a restricted passage and, likewise, the piston 3 may be raised in the cylinder 4 with the oil displaced from the head end flowing into the rod end and excess oil passing into the tank 10 through the aforesaid restricted passage.

Having thus described the hydraulic circuit of FIG. 1, reference will now be made in detail to FIG. 2, and to the manner of its operation in relation to the operation of the directional control valve 15 and the fluid motor 1.

(a) The raise operation When it is desired to move the piston 3 upwardly in the cylinder 4 thus to lift the scraper bowl or like implement, the valve spool 16 will be shifted to the R position, whereby oil under pressure supplied to the inlet port 14 will flow through the upper motor port 19 and through the conduit 21 into the port 8 at the rod end of the cylinder 4, and as the piston 3 is urged upwardly by such fluid pressure, the displaced fluid will flow out of the cylinder 4 into the tank 10 via passage 23 in housing 24, bore 25 of a pilot valve 26, port 7, conduit 20, lower motor port 18, and return port 17 It is noted that the passage 27, 27', 27 in the housing 24 leading from the head end of cylinder 4 to the port 6 has therein a pressure-seated pilot operated check valve 28 which closes the passages portion 27" from the passage portion 27'. The check valve 28 is seated, not only by the force of the spring 29, but also by fluid pressure in the chamber 30, the pressure in the port 6 and passage portion 27" entering the chamber 30 through an orifice 31. Thus, when the directional control valve spool 16 is in the raise R position, the check valve 28 will not open regardless of the magnitude of the fluid pressure, since the fluid under pressure in the chamber 30 acts on the area of the seat 32.

(b) The lower operation for quick dumping When the valve spool 16 is shifted to the lower L position, the inlet port 14 is communicated with the lower motor port 18 whereby fluid under pressure flows into the head end of the cylinder 4 via conduit 20, port 7, bore 25, and passage 23 thus to cause downward movement of the piston 3, and the fluid displaced from the rod end of the cylinder 4 is returned to the tank 10 via port 8, conduit 21, upper motor port 19, and return port 17. If there is a heavy downward load on the piston 3 which it is desired to quickly dump, the increased rate of flow (and thus increasing pressure drop) through the bore 25 of the pilot valve 26 will cause the latter to move downwardly against the spring 34. When the rate of flow of fluid into the head end of the cylinder 4 reaches a predetermined amount, the openings 35 and 36 in the pilot valve 26 and in the fixed sleeve 37, will be in alignment thus to permit flow of fluid from the chamber 30 through the passages 38, 39, and 40, faster than fluid can be replenished through the orifice 31. When that occurs, the check valve 28 will be forced downwardly against the spring 29 and away from the seat 32 and the then predominating pressure in the port 6, and passage portions 27" and 27' will open another check valve 41 against its biasing spring 42 to allow the displaced fluid from the rod end of the cylinder 4 to enter the head end of the cylinder 4 via the passage 27"-27'-27. In this way, the piston 3 may be moved very rapidly in the cylinder 4 at a rate exceeding pump capacity without causing cavitation.

(c) Power lower operation with upward reaction on piston 3 Under this condition of operation as the piston 3 movement slows down, the resulting build up of pressure in the head end of the cylinder 4 will immediately seat the check valve 41 and, of course, the reduced rate of flow of fluid into the head end of the cylinder 4 through the sleeve bore 25 of the pilot valve 26 will permit movement of the latter by the spring 34 to a position wherein the openings 35 and 36 are out of alignment so that pressure in the passage portion 27" and in the chamber 30 will again equalize through the orifice 31 to cause seating of the check valve 28 under the influence of the spring 29 and fluid pressure in chamber 30.

At the point where the openings 35 and 36 are yet in alignment, and as the pressure builds up, there will be leakage of fluid through the openings 35 and 36, passages 40, 39, and 38, chamber 30, and orifice 31 back into the return side of the system. If such fluid loss is objectionable, a check valve 45 may be provided in the orifice 31 as shown in FIG. 3.

(d) The float operation In systems which require a float position, the directional control valve spool 16 will be provided with a float F position wherein the lower and upper motor ports 18 and 19 are communicated with one another within the directional control valve 15 and in that case, if the head end of the cylinder 4 demands a rate of flow equal to the predetermined rate through the bore 25 of the pilot valve 26, the flow from the rod end port 8 will be diverted as described under (b) Lower operation for quick dumping, thus again to prevent cavitation.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In combination, a double acting fluid motor; a pump; a tank; valve means; and conduit means operatively interconnecting said motor, pump, tank, and valve means whereby fluid pressure actuation of said motor is controlled by said valve means; said valve means including a directional control valve having an operating position wherein fluid under pressure delivered by said pump to said directional control valve is conducted through a first passage to one end of said motor and wherein returning fluid displaced by the other end of said motor is conducted through a second passage to said tank, said second passage having a branch passage also leading to said one end of said motor; flow responsive means in said first passage; a check valve in said branch passage opened responsive to predetermined rate of flow through said flow responsive means thus to permit returning fluid to augment the incoming fluid into said one end of said motor to achieve rapid actuation of said motor.

2. The combination of claim 1 wherein another check valve in said branch passage opens to permit flow as aforesaid but closes to prevent reverse flow of fluid as the pressure of the fluid in said one end of said motor builds up.

3. The combination of claim 1 wherein said check valve is of the pilot operated pressure-seated type; and wherein said flow responsive means constitutes a pilot valve operative upon predetermined rate of flow therethrough to bleed fluid from a pressure chamber behind said check valve more rapidly than fluid can be replenished into the chamber from an orifice communicating the chamber with said branch passage.

4. The combination of claim 3 wherein said pilot valve comprises a tubular sleeve through which incoming fluid flows into said one end of said motor, said sleeve upon predetermined rate of flow of fluid therethrough being moved by the resulting pressure drop to a position wherein an opening therein communicates with such chamber.

5. The combination of claim 1 wherein the portion of said valve means containing said first passage and said branch passage is a valve housing secured to said one end of said motor.

6. The combination of claim 5 wherein said check valve and said flow responsive means are movably supported in said housing.

7. The combination of claim 6 wherein said flow responsive means constitutes a pilot valve operative upon predetermined rate of flow therethrough of bleed fluid from a pressure chamber behind said check valve more rapidly than fluid can be replenished into the chamber from an orifice communicating the chamber with said branch passage.

8. The combination of claim 7 wherein said pilot valve comprises a tubular sleeve through which incoming fluid flows into said one end of said motor, said sleeve upon predetermined rate of flow of fluid therethrough being moved by the resulting pressure drop to a position wherein an opening therein communicates with such chamber.

9. The combination of claim 7 wherein another check valve in said branch passage opens to permit flow as aforesaid but closes to prevent reverse flow of fluid as the pressure of the fluid in said one end of said motor builds up.

'10. A valve assembly for use in a hydraulic circuit for controlling the actuation of a double acting fluid motor comprising a housing having first and second passages for flow of fluid therethrough; a pilot operated check valve in said second passage; a pilot valve in said first passage operative upon predetermined rate of flow in one direction in said first passage to open said check valve for flow of fluid in one direction in said second passage.

11. The valve assembly of claim 10 wherein another check valve in said second passage downstream of said pilot operated check valve prevents flow of fluid in the opposite direction in said second passage.

12. The valve assembly of claim 10 wherein said check valve is of the pressure-seated type; and wherein said pilot valve is movable in said first passage responsive to predetermined rate of flow of fluid therethrough to a position where it bleeds fluid from a pressure chamber behind said check valve more rapidly than fluid is replenished in said chamber through an orifice communicating said chamber with said second passage.

13. The valve assembly of claim 12 wherein said pilot valve is a tubular sleeve movable in said housing responsive to increasing rate of flow of fluid therethrough, said sleeve having an opening therein which registers with a passage leading to said chamber at a predetermined rate of flow thus to bleed fluid from said chamber as aforesaid.

14. The valve assembly of claim 10 wherein said pilot valve, upon reversal of flow of fluid in said first passage, is inoperative to open said check valve.

15. The valve assembly of claim 14 wherein another check valve in said second passage downstream of said pilot operated check valve prevents flow of fluid in the opposite direction in said second passage while fluid flows in said one direction in said first passage.

References Cited UNITED STATES PATENTS 2,267,284 12/ 1941 Livers 91-436 2,367,682 l/1945 Kehle 91-436 2,608,824 9/1952 Kirkham. 2,646,025 7/1953 Deardorff 91-436 2,980,135 4/1961 Tennis 137-59612 3,267,961 8/1966 Rice 91-436 FOREIGN PATENTS 863,701 3/1961 Great Britain.

EDGAR W. GEOGHEGA'N, Primary Examiner US. Cl. X.R. 

